System of motor control.



PATENTED JULY 26, 1904.

A. '0; EASTWOOD. sYsTBM 0F MOTOR 001mm.

APPLICATION FILED APR.19. 1904.

N0 MODEL.

Wilma UNITED STATES Patented July 26, 1904.

ARTHUR C. EASTWOOD, OF CLEVELAND, OHIO.

SYSTEM OF MOTOR CONTROL.

3PEGIFICATION forming part of Letters Patent No. 756,104, dated July 26,1904.

Application filed April 19, 1904:.

T0 aZZ whom it may concern.-

Be it known that I, ARTHUR O. EASTWOOD, a citizen of the United States,residing in Cleveland, Ohio, have invented certain Improvements inSystems of Motor Control, of

which the following is a specification.

The object of my invention is to provide a novel combination ofapparatus which will permit the speed of a motor, as Well as itsreversal and the braking force applied to it and its load for bothdirections of operation, to be governed by a controller having a singleopcrating-lever.

It is further desired to provide a system for controlling the operationof an electric motor which shall be both simple as to the connection andarrangement of its parts and of such a nature as to be particularlyadapted to the rapid operation of high-speed apparatus.

An additional object of my invention is to provide a controlling systemin which will be combined the means for governing the speed of a motorwhen current is applied thereto and also means for applying a variablebraking force to said motor after the current-supply is cut off. i

It is further desired to provide a system in which the energy stored upin the armature of the motor and its attached moving parts due to theirmotion shall be absorbed and dissipated with practically no wear ordepreciation of the apparatus employed. it being also desired that theenergy liberated in lowering a load under the action of gravity shall beabsorbed and dissipated without the use of mechanical brakes.

These objects I attain as hereinafter set forth, reference being had tothe accompanying drawings, in Which Figure l is a diagrammatic viewshowing the preferred arrangement and connections of the apparatuscomprising my system of control; and Fig. 2 is a sectional plan view ofportions of two switch-blades and their supporting structure, showing mypreferred device for permitting but one of said two switches to beclosed at the same time.

In the past electrical motors for driving cranes, conveying bridges, andsimilar ma- Serial No. 203,881. (No model.)

chinery have been almost universally controlled by manually-operatedcontrollers so designed that all of the main circuit connections forstarting the motor and cutting in and out resistance have been effectedby hand. The motors have in general been provided with electromagneticbrakes released by the flow of current through a magnetizing-coil andapplied by a weight or spring, the connections oi' the coil beingusually so arranged that when current is cut off from the motor thebrake isautomatically applied.

Of late years the speed and power of the above mentioned class ofmachinery have been so far increased that motors of from onehundred tothree-hundred horse power are very frequently employed, such motorsbeing governed by 1nanually-operated controllers. These latter arenecessarily of very large size and require great physical effort fortheir operation, particularly when it is desired to secure a high speedof operation of the machinery actuated from the driving-motor. As aconsequence, the operator is frequently overworked, so that in manycases the output of the machinery is limited by his physical end urancein manipulating the controller.

The heavy conductors for transmittingcurrent between the controller andthe motor become under ordinary conditions an item of considerableexpense, particularly if there is relative motion between the operatorand the motor under his control, which necessitates carrying the currentthrough sliding or rolling connections. Further, each time the motor isbrought up to speed an amount of energy is stored in the armature andother moving parts of the system, which energy must be absorbed anddissipated each time the motor is brought to rest. When the machineso'perated are of large size and operated at frequent intervals there isconsequently considerable heating, as well as rapid wear anddepreciation of the brakes, thus necessitating the expenditure of muchtime and labor for their adjustment and their repair. Again, since nopractical way has hitherto been devised for controlling the brakingforce of a solenoid-brake and as such brake must be adjusted to hold aload after it has stopped the same the motor and apparatus connectedthereto are usually brought to rest with a jerk, producing what may beinjurious strains. In some instances it has been customary to employworm-gears for controlling the lowering of a load, which gears are ofsuch a pitch that they must be driven in order to permit the load todescend.

The energy delivered by the lowering of a load must necessarily beabsorbed by the worm-gearing, and as the efliciency of this latter isthe same both in hoisting and in lowering a large amount of power isconsequently required to hoist said load. It will therefore be seen thatthis arrangement of apparatus is exceedingly wasteful of power.Mechanical brakes, in connection with spur-gear drives, have also beenemployed for governing the descent of a load; but, as above pointed outin connectionwith solenoid-brakes, the wear and heating due to the largeamounts of energy handled as well .as to the high speed of operationproduce very rapid depreciation of such brakes.

By my invention I employ magneticallyoperated switches for effecting allof the necessary connections for stopping, starting, and reversing themotor as well as for cutting in and out the resistance used incontrolling the speed of the motor. Not only are said switches andcontrolling resistance placed adjacent to the motor, so as to do awaywith long conductors of large size, but the operating-controller isconstructed to carry only sufficient current to energize themagnetizing-coils of the various switches, its wiring connections beingtherefore of small size. Further, the controller itself may be maderelatively small and compact and can be operated with the greatest ease.

I further provide switches and connections, as well as contacts on theoperating-controller for energizing the coils of said switches, by meansof which when the motor is disconnected from its normal source ofcurrent the electrical apparatus of the system may be reconnected in aclosed circuit independent of said sources, so that the motor willoperate as a generator. I also provide means whereby the resistance incircuit when the motor is operating as a generator may be varied at willto vary the current delivered, and consequently the braking forceexerted upon the motor-armature and the machinery driving the same. Forthis purpose I prefer to use either the whole or a part of the ordinarycontrolling resistance of the motor, which, being preferably formed ofcast-metal grids, will absorb and convert the energy of the moving ma-.chinery into heat with practically no wear or depreciation. In securingthis last-described action I preferably use certain of themagnetically-operated switches normally employed for reversing andcontrolling the speed of the motor to effect the braking of the motor,as well as to control the amount of such braking,

it being consequently seen that the addition of the braking attachmentto the apparatus of my system adds but little to the cost of the same.

In order to hold a load when the motor is out of operation, I preferablyemploy a solenoid-brake so connected that while normally it takes nopart in retarding the armature or the machinery connected thereto itimmediately becomes effective for holding motionless said parts as soonas current no longer flows to or from the motor.

In the above drawings, A represents a compound-wound motor having anarmature a, with a shunt field-winding a and a series fieldwinding a abeing the coil of a solenoidbrake connected in series with said serieswinding. B is the operating-controller, which is shown in the drawingswith its revoluble cylinder as developed.

There are in the present instance ten contact-fingers 1 to 10,inclusive, upon this controller and two sets of contact-segments b andbupon the cylinder coacting therewith, it being noted that all of thesegments of each set are respectively in electrical connection with eachother. In the off position of the controller the fingers are between andout of contact with the segments of the two sets. 0, c,

2 3 c and c are banks of resistance, preferably in the form of grids ofcast metal, connected, respectively, to four switches and to each other,as shown.

In the present instance I preferably employ thirteenmagnetically-operated switches, (designated by the letters D to P,inclusive,) each provided with a magnet-coil whose energization closesthe switch.

It will be seen that the switches D and E, F and Gr, H and I, and O andP have extending between their blades a pivotally-mounted locking-bar Q,preferably of the construction shown in Fig. 2. This bar is placed sothat its ends extend under the blades of two adjacent switches as D andE, for examplebe ing supported upon a standard q, suitably held to theswitchboard g and insulated from said blades in any desired manner. Saidbar is held at such a height that when one of the switch-blades is movedunder the action of its magnet, so as to form electrical connectionbetween its respective terminals, the blade of the other switch engagedby the bar is necessarily moved out of engagement with its terminals.Moreover, the various parts are so arranged that even if the magneticcoil of this second switch be energized the blades of said switch cannotbe closed until the coil of the first switch has been deenergized andits blade brought to an open position.

The switches D, E, F, and Gr when considered together constitute thereversing-switch of the motor, and it will be seen that the switches Dand Gr will close simultaneously, since their coils are both connectedto a comfield=windings remaining unchanged.

mon contact-finger 2 of the controller B. Similarly the switches E and Fwill close together, since their operating magnet-coils are bothconnected to the same contact-finger 1. It will be seen, however, thatboth of these pairs of switches cannot be closed at the same time,since'one switch of each pair has extending between its blade and theblade of a switch of the second pair one of the locking-bars Q.

The connections between the switches D to G, inclusive, are such thatwith the switches D and G closed current will flow through the armatureof the motor in one direction, while with the switches E and F closedcurrent will flow through said armature in an opposite direction, thedirection of the current in the It will be seen that the shuntfield-winding is permanently connected between the positive and negativesupply-mains.

The switches O and Iserve as main switches to cut ofi the motor from thesupply-mains,

it being noted, however, that both the shunt field-winding and thevarious connections for the magnetic coils of the switches are connectedto the live sides of these switches.

Switches J, K, L, and M, respectively, control the four banks ofresistance 0, 0, c and 0 the connections being such that when the switchJ is closed the resistance cis in circuit with the motor, while with theswitches J and K closed the two resistances cand 0 will be in multiplewith each other and together in series with the motor. ing of theswitches L and M successively throws the resistances 0 and c in multiplewith the other resistances 0 and c, with the result that each additionalbank of resistance thrown into circuit reduces the combined resistancein circuit with the motor while increasing the carrying capacity of thisport-ion of the circuit.

The switches H and P serve to close the circuit of the motor during theaction of braking and are respectively interlocked with the mainswitches I and O, so that by no possibility can these latter be closedat the same time as are said switches H and P.

The switches F, Ur, J, K, L, M, O, and P are each provided withauxiliary terminals f g. &c., which are electrically connected'bysuitably-placed metallic pieces f and g, &c., carried by but insulatedfrom the blades of these switches when said blades are in their closedpositions. The functions of these auxiliary switches will be noted inconnection with the description of the operation of the system.

Considering the motor at rest, the turning of the barrel of theoperating-controller B to the first point, so as to bring the segments 6into engagement with the fingers of said controller, will cause theswitches E, F, H, J, K, L, M, and P to be closed. there being, however,no flow of current through the Similarly the closmain circuit, becausethe main switches I and O remain open. On the second point it will beseen that there is no longer a segment in engagement with the finger 8of the controller B, and since this deenergizes the coil of the switch Jsaid switch opens. On the second and third points the circuits includingthe fingers 6 and 7 are successively open-circuited, thus causing theswitches K and L to open, while on the fourth point the fingers 2 and 4:are supplied with current by contact with suitable segments on thecontroller-barrel, and the coils of switches D and G are consequentlyenergized. Said switches cannot, however, close, since the blades of theswitches E and F, through their respective locking-bars Q, preventmotion of the blades of said switches D and Gr. Similarly, though thecoils of switches I and O are energized, switches P and H, being closed,effectually prevent the closing of said main switches. As soon, however,as the continued motion of the barrel of the controller B causes thesegments hitherto in engagement with the fingers 1 and 3 to breakcontact with the same the coils of the switches D, G, H, and P aredeenergized, and consequently the four switches E, F, I, and O at onceclose under the action of their respective coils. Since the switch M hasremained closed from the beginning, current will now flow through themotor, passing from the positive supply -main to the switch O, throughthe bank of resistance 0 switch M, switch G, armature a, switch D, coil(0 of the solenoidbrake, series winding a of the motor, lower terminalof switch H, and through switchI to the negative supply-main. Thepassage of current through the coil (6 causes the brake controlledthereby to be released, and conse-' quentl y the motor will start andoperate its at tached machinery in the well-known manner.

As the barrel of the controller B is turned to its next point the finger6 of said controller is again supplied with current and ener gizes thecoil of the switch L. The closing of this latter switch throws the bankof resistance into multiple with the resistance 0 which by reducing thecombined resistance in circuit with the motor permits this latter toreceive more current and to operate at a higher speed. On succeedingpoints of the controller the speed of the motor is still furtherincreased by the successive placing of the banks of resistance 0 and cin multiple with the resistance previously in circuit until on the lastpoint the finger 9 of the controller B is supplied with current and thecoil of the switch N is energized. The closing of this switchshort-circuits all of the resistance, so

that the motor is supplied with current direct from the mains and willoperate at full speed. If now the barrel of the controller B is turnedin a reverse direction, the switches N, J, K, and L will successivelyopen, gradually increasing the effective resistance in circuit with themotor and reducing its speed. After the opening of the switch L it willbe seen that the fingers 1 and 3 of the controller are again suppliedwith current, thereby energizing the coils of the switches E and F and Hand P. As soon, therefore, as the contactfiugers 2 and t no longer,engage their respective segments switches D and G and I and O are openedand the switches E, F, H, and P are immediately thereafter closed. Underthese conditions it will be seen that the motor is short-circuited uponitself, and since its armature is still turning either under the actionof the machinery attached to it or by means of its own momentum currentwill be generated and will consequently retard such revolution. The pathof this current will be from the armature a to the switch E, coil (0series field a switch H, resistance 0 switch M. switch F, and back tothe armature.

It will be seen that by causing the switches E, F, H, and P to closeimmediately after the switches 1), G. l, and 0 have been opened there ispractically no cessation of current through the coil a so that thesolenoid brake mechanism still remains in its released position. Thecontinued motion of the barrel of the controller B toward its offposition gradually increases the braking effect upon the motor by reasonof the successive closing of the switches L, K, and J, which place theresistance 0. 0, and c in multiple with the resistance 0 thus permittingincreased current to flow through the circuit. Under these circumstancesthe armature of the motor is very quickly brought to rest, and since assoon as its motion ceases there is no further flow of current throughthe coil a the brake will be instantly applied, so as to hold the loadfrom further motion. From the above it will be seen that not only theoperating speed of the motor, but the retardation exerted by the same inbringing a load to. rest, is completely under the control of anoperator.

The movementofthe barrel ofthe controller B to the other side of its offposition and its re turn to said ofi position produces the same cycle ofoperations as that hithereto described, with the exception that thedirection of rotation of the armature is reversed.

It will be noted that among the segments of the controller B there isnone for causing the closing of the switch N after the various banks ofresistance have been thrown in to increase the braking action of themotor. This is done in order'to limit the maximum braking-current whichmay be generated by the motor.

The various auxiliary switches above noted are so connected that themain switches are interlocked when current is supplied to the motor,said main switches being necessarily closed in the following order inspeeding the motor viz switches F or G, O, M, L, K, and Jand when thecontroller B is operated to retard the action of the motor in thefollowing orderviz., switches F or G, P, M, L, K, and J.

I claim as my invention 1. The combination of a motor, a switch orswitches for reversing the direction of current-flow through one of themembers of said motor, another switch or switches for closing thecircuit of the motor independently of the supply-mains and a controllerhaving fingers and two series of contacts, with connections between theswitches and the controller so arranged that the contacts in eitherseries first engaged by the fingers will cause operation of the switchesfor short-circuiting the motor, substantially as described.

2. The combination of a motor, an electromagnetic switch or switches forconnecting the same to supply-mains, another electromagnetic switch orswitches for connecting said motor in a closed circuit independent ofsaid mains, witha motor-reversing device connected to operate saidsupply switch or switches only after the short-circuiting switch orswitches have been operated as said device is moved in either directionfrom its off position, and mechanism for keeping open one switch or setof switches as long as the other set is closed, substantially asdescribed.

3. The combination of a motor, switches, and a controller for operatingsaid switches, said controller having contact-fingers and contacts, saidcontacts being arranged and connected on each side of the fingers sothat the switches will be operated to successively brake and acceleratethe motor as the controller is operated in either direction from its offposition. substantially as described.

4:. The combination of a motor, a reversing switch or switches; ashort-circuiting switch or switches, a bank of resistance, a switch forcontrolling the introduction of said resistance into circuit with themotor and a controller for operating said switches, said controllerhaving contacts for causing the resistancecontrolling switch to closeboth when the motor is receiving current from the supplymains and whenit is in a closed circuit independent of said mains, substantially asdescribed.

5. The combination of a motor, switches for accelerating, braking andreversing the same, a controller including fingers and a plurality ofseries of contacts, with connections between said switches and thecontroller so arranged that the braking-switches are'actuated before theaccelerating-switches, substantially as described.

6. The combination of a motor, switches for accelerating, braking andreversing the same, a controller including fingers and a plurality ofseries of contacts, with connections between said switches and thecontroller so arranged that the braking-switches are actuated before theaccelerating-switches, as said controller is operated in eitherdirection from its ofi? position, substantially as described.

7 The combination of a motor, acoil having a brake, in circuittherewith, a switch or switches for connecting the motor tosupplyrnains, a switch or switches for connecting the motor in a closedcircut independently of said mains and a controller for actuating saidswitches, substantially as described.

8. The combination of a compound-wound motor, a coil for a brake incircuit with the series winding thereof and a switch or switches forconnecting the motor to supply-mains, a

switch or switches for connecting the motor in a closed circuitindependently of said mains and a controller for actuating saidswitches, substantially as described.

9. The combination of amotor with a switch or switches for connectingthe same to supplymains, another switch or switches for connecting themotor in a closed circuit independently of said supply-mains, with acontroller for operating said switches, said controller having itscontacts so connected as to actuate said switch or switches forconnecting the motor in a closed circuit,before the other switches areactuated, as said controller is operated from its off position,substantially as described.

" 10. The combination of amotor with means for governing the flow ofcurrent through the same, said means including a controller havingfingers and contacts so placed that operation of said controller ineither direction from its ofi position first connects said motor in aclosed circuit and afterward connects it to the current-supply mains,substantially as described.

11. The combination of a motor with means for governing the flow ofcurrent thereto, said means including a controller having fingers and amovable structure actuated from a sin-' gle movable part, said structurehaving contacts so placed that operation of said part in eitherdirection from its off position first connects said motor in a closedcircuit and afterward connects it to current-supply mains, substantiallyas described.

12. The combination of a motor with means for governing the flow ofcurrent thereto, said means including a controller having fingers andcontacts so placed that operation of the movable element of thecontroller in one direction from its off position first connects saidmotor in a closed circuit and afterward connects it to the supply-mains,while operation of the controller in the opposite direction from saidoil position reverses the motor and successively connects it in a closedcircuit and to the supply-mains, substantially as described.

13. The combination of a motor, a series of switches for reversing thesame, a switch or switches for connecting the motor to supplymains.another switch or switches for connect ing the motor in a circuitindependent of said supply-mains, with an interlocking device or devicesbetween the supply-switches and the short-circuiting switches, andbetween certain of the reversing-switches, substantially as described.

14. The combination of a motor, banks of resistance, switches forthrowing the same into circuit, a switch or switches for connecting themotor to supply-mains, a switch or switches for connecting the motor ina closed circuit independent of said mains and a controller for saidswitches including contacts whereby the resistance-controlling switchesare made to operate both when the motor is short-circuited and when itis receiving current from the supply-mains, substantially as described.

15. The combination of a motor, banks of resistance, switches forthrowing said resistance into circuit, means for connecting the motor tosupply-mains, means for connecting the motor in a closed circuitindependent of said means, a switch for short-circuiting saidresistance, with a controller for operating said switches,saidcontroller being constructed to actuate the resistance-controllingswitches both when the motor is connected to the supply-mains and whenit is connected in a circuit independent of said means, the switch forshort-circuiting said resistance being operated only when the motor isconnected to the supply-mains, substantially as described.

16. The combination of a motor, switches for controlling the operationthereof, with a pivoted bar free to turn in a plane substantially atright angles to the planes of motion of the switch-blades and having itsends respectively operative upon two switch-blades to prevent both ofsaid blades being in a closed position at the same time, substantiallyas described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

ARTHUR C. EASTWOOD.

